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Natural ventilation

Ventilation is of the utmost importance to ensure an adequate quality of indoor air, since it allows to renew the air in a home, thus minimizing health problems related to humidity and mold, pathologies that normally appear in homes with poor ventilation.

The vast majority of Portuguese buildings have natural ventilation, that is, they promote ventilation inside spaces without the use of mechanical equipment, which on the one hand allows to reduce the costs associated with this parameter, but on the other hand makes it difficult to ensure a renovation value. adequate air.

How does ventilation work in a home?

Ventilation can be natural, mechanical or mixed, depending on the type of equipment that promotes it.

  • In the case of natural ventilation, it occurs through openings in the surroundings, windows and / or other holes for this purpose, and the extraction of air occurs through chimneys;
  • In the case of mechanical ventilation, there are extractors that operate 24 hours a day to ensure the insufflation and extraction of air, varying the air extraction capacity that these facilities have throughout the day, for example, during peak hours there is a greater capacity for extraction to cope with baths and meals, making it necessary to inflate and extract a greater amount of air.
  • Mixed ventilation occurs when there is natural and mechanical ventilation, that is, fresh air enters through the openings in the surroundings and is extracted through exhaust fans and extractors in the bathroom.

Mechanical ventilation ensures better control over air renewal conditions, however, there are costs associated with the operation of the equipment that must be evaluated in a cost-benefit analysis of the solution.

Consumo de energia na ventilação

A ventilação é responsável por aproximadamente 50% das perdas de energia numa habitação. Quanto maior a quantidade de ar renovada por hora, maior será o consumo de energia.

Reduzir a ventilação natural

Em casas com janelas de correr ou degradadas, ocorrem infiltrações de ar acima do desejável. Pode reduzir a renovação do ar interior (para valores entre 0,4 e 0,6 Rph), substituindo ou reparando as janelas existentes.


Reduzindo as renovações de ar por hora para valores entre 0,4 e 0,6 Rph, é possível reduzir o consumo de energia com a climatização em 25%.

Important tips
  1. In natural ventilation, air inlets and outlets are important for it to circulate. The windows must have adequate openings and the air vents in the bathrooms must be unobstructed;
  2. The doors of rooms between which drains air (eg kitchens, toilets) must have grilles or gaps close to the floor (about 1 cm on the doors of rooms and toilets and 2 cm on the kitchen door);
  3. As it is not possible to install mechanical ventilation in all houses, it is necessary to evaluate the air inlets and outlets and carry out a specific study for this purpose. The introduction of mechanical fans must be carried out by experienced professionals;
  4. Ventilation also ensures the proper functioning of firing devices (fireplaces, stoves, etc.);
  5. Air infiltrations through the slits should be reduced. Over time, some of the equipment and construction materials in our housing begin to deteriorate and show slack. The windows, doors and shutters are an example of this. These situations can be solved with insulation bars or caulking tapes;
  6. If your house has an energy certificate, evaluate the solutions proposed by the qualified expert.
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